Variable-tone electronic alarm system

ABSTRACT

An intrusion alarm having an audio oscillator capable of producing fixed or variable frequency tones wherein closing of an intrusion detection switch causes the oscillator to first deliver a fixed warning tone to a local loudspeaker, and after a time delay causes the oscillator to deliver a variable frequency alarm tone to the local and a remote loudspeaker in the event authorized deactivation of the alarm system does not take place before expiration of the time delay period. Fire and panic switches provide for immediate alarm tone signalling by bypassing the time delay circuit.

United States Patent Horton Aug. 8, 1972 54] VARIABLE-TONE ELECTRONIC 3,355,706 1 1 1967 Pitches ..340/384 E x ALARM SYSTEM 3,402,329 9/1968 Stewart ..340/329 x Inventor:

[72] Charles A. Horton, 3210 Bluebonnet, Houston, Tex. 77025 Filed: March 1, 1971 App1.No.: 119,764

References Cited UNITED STATES PATENTS 11/1965 Foster ..340/384 E X 10/1968 Blivice et al. ..340/276 12/1970 McMann et al ..340/328 X Primary Examiner-David L. Trafton Attorney-Michael P. Breston and Alfred B. Levine [57] ABSTRACT An intrusion alarm having an audio oscillator capable of producing fixed or variable frequency tones wherein closing of an intrusion detection switch causes the oscillator to first deliver a fixed warning tone to a localloudspeaker, and after a time delay causes the oscillator to deliver a variable frequency alarm tone to the local and a remote loudspeaker in the event authorized deactivation of the alarm system does not take place before expiration of the time delay period. Fire and panic switches provide for immediate alarm tone signalling by bypassing the time delay cir cuit.

10 Claims, 1 Drawing Figure 11 13 5| SCR H5 1s r68 7 J 51 7 27 2 11111 DELAY 11AM 112111011 64 ZZ\ 25 24 36 (0'55SEBONDS1 51k VARIABLE Y QL A 58 1111110 VOLTAGE N s AMPUHER souncs 05011111011 as 62 as 48 so so 344 ivvwuivu -T new PATENTEDAus 8 m2 In f 2 m M 55:: A s N 22:; 2 W m A .I :5 V y. iwnm g on mm 3 :33 22;: mm $2 363 35:; A 51:22 A My 252:: 35:; mm 3 222 mm 32;; 522: 3 m $23: 3 3 3 Z 2 MN 3 zzoahwz i g 2:; E: Z N g f I 2 Z m I N. a 2 21. W km 3 3 :w m U 2 2 Z 2 MICHAEL P. BRESTON ATTORNEY.

VARIABLE-TONE ELECTRONIC ALARM SYSTEM This invention provides a variable-tone electronic alarm system capable of detecting the unauthorized entry into guarded premises as well as other undesired events such as fires, etc. The system includes a variable-frequency oscillator which generates a singlefrequency warning tone inside the guarded premises upon the closure of a detector switch. If after a predetermined time-delay interval the alarm system is not turned off, then the oscillator will produce a variable-frequency alarm tone both inside and outside of the guarded premises.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION This invention provides a variable-tone intruder detection system including a variable-frequency oscillator which, upon the closure of a detector switch, sounds a single-frequency or warning monotone having an intensity which makes it audible primarily inside the guarded premises. The owner upon hearing the warning signal can, during a predetermined time interval, turn the system off in the event of a false warning signal. If the system is not turned off, the variable-frequency oscillator then generates a variable-frequency alarm tone which is radiated both indoors and outdoors to alert passerbys and neighbors of the occurrence of an emergency.

It is an object of this invention to provide an electronic intruder system which is not offensive to neighbors upon the occurrence of false alarms.

It is another object of this invention to provide such an intruder system which is relatively inexpensive to manufacture, which is easy to install, and which requires a minimum of standby power.

BRIEF DESCRIPTION OF THE DRAWING In the drawing the sole F IGUREshows in block diagram form a preferred embodiment of the present invention for first generating an indoor warning audio signal and then an alarm signal.

In the drawing the electronic intruder system is generally designated as and includes a first pair of terminals 12 and 14 and a second pair of terminals 16 and 18. Between terminals 12 and 16 is a conductor 17 and between terminals 14 and 18 is a conductor 19. Terminal 14 is connected to ground 20. Connected in parallel-circuit arrangement across lines 17 and 19 are: a variable-voltage source 22, a variable-frequency oscillator 24, an audio amplifier 26, and a time-delay network 28.

The variable-voltage source may be a saw-tooth oscillator having a voltage-control terminal 30. When a suitable voltage is applied to terminal 30, the voltage on terminal 30 will vary between an upper level 23 and a lower level 25 following a saw-tooth waveform 27.

Terminal 30 is connected to a frequency-control terminal 34 in the variable-frequency oscillator 24. Oscillator 24 provides to its output terminal 36 a singlefrequency or monotone 37, say on the order of 1,000 Hz. On the other hand, when the saw'tooth waveform 27 is applied to the frequency-control terminal 34, oscillator 24 will generate an audio alarm signal having a frequency range, say between 300 to 3,000 Hz, herein called the variable tone" 39.

The output terminal 36 from the variable-frequency oscillator 24 is coupled to the input terminal 38 of the audio amplifier 26 having an output terminal 40. Hence, either the monotone or the variable tone will appear at the output terminal 40 depending on the nature of the signal applied to the input terminal 38 of the audio amplifier 26.

Connected in parallel-circuit arrangement between terminal 40 and ground 20 are: a first sound producer such as an indoor speaker 42, and a second sound producer such as an outdoor speaker 44. In series with speaker 44 are a pair of relay terminals 46, 48 which are controlled by a DC relay 50. Relay 50 is connected between the cathode 52 of a silicon-controlled rectifier (SCR) 51 and grounded terminal 18. A conductor line 54 also connects cathode 52 to the voltage-control terminal 30 for a purpose subsequently explained.

To energize the alarm system 10 there is provided a DC battery having its negative terminal 62 connected to ground 20 and its positive terminal 64 connected to a transmission line 66 through an ON-OFF power switch 68. Transmission line 66 includes a plurality (only two are shown) of normally OFF detector switches 70 which are placed in conventional manner around monitored objects such as doors, windows, safes, etc.

Also connected between the positive terminal 64 and the gate of SCR 51 is an auxiliary transmission line 72 which may include a thermal switch 74, a panic button 76, etc., both normally OFF. The anode 67 of SCR 51 is connected to terminal 16. Gate 65 is connected to the gate 69 of another SCR 71, whose anode 73 is connected to terminal 64 via switch 68, and whose cathode 75 is connected to terminal 12.

In operation of the alarm system 10, when the owner desires for the system 10 to survey the guarded premises he closes switch 68. When an unauthorized entry occurs, one or more of switches will close, thereby applying the battery voltage to gate 73, firing SCR 71, and energizing lines 17 and 19. This energizes the variable-voltage source 22, the variable-frequency oscillator 24, the audio amplifier 26, and the time-delay network 28. Accordingly, oscillator 24 will produce its monotone or single-frequency warning signal 37. The warning signal 37 after being amplified by the audio amplifier 26 is applied to speaker 42 for sounding an indoor warning signal throughout the guarded premises. Upon hearing the warning signal, the owner can, within a predetermined time-delay interval, turn off the power switch 68 thereby de-energizing the alarm system 10. This is normally done when the warning signal 37 is known to be a false alarm.

If on the other hand the owner does not turn off power switch 68, then after the predetermined time interval, which in a preferred embodiment could be adjusted in the time-delay network 28 between and 55 seconds, the gate 65 will receive a voltage from and through the time-delay network 28. This voltage will fire the SCR 51 thereby energizing relay 50 and closing contacts 46, 48. Upon closing of relay contacts 46 and 48, the outdoor speaker 44 becomes connected to the output terminal 40 of the audio amplifier 26. At the same time as relay 50 becomes energized, the voltage which appears on cathode 52 is also applied via auxiliary line 54 to the voltage-control terminal 30 of the variable-voltage source 22. The voltage on terminal 30, and hence on terminal 34, starts oscillating as shown by the saw-tooth signal 27. The saw-tooth signal 27 which is applied to the frequency-control terminal 34 causes the variable-frequency oscillator 24 to produce the variable-frequency signal 39. Signal 39 after being amplified by the audio amplifier 26 becomes applied to both speakers 42 and 44 for sounding an alarm both indoors and outdoors of the guarded premises.

The auxiliary line 72 also allows the use of the alarm system for heat or fire detection, as well as for the detection of other monitored conditions. When, for example, a heat detector switch 74 closes, then the battery voltage is applied directly to gates 65 and 69 thereby causing, in a manner previously explained, the generation of the variable tone 39 by the variablefrequency oscillator 24. After the battery voltage is applied to gates 65 and 69, relay 50 becomes energized thereby closing relay contacts 46 and 48.-Accordingly, the amplified, variable-frequency alarm signal 39 becomes instantaneously (without delay) applied both to the indoor and outdoor speakers 42 and 44 for sounding an alarm in the event of a fire or other monitored condition.

While this invention has been described in connection with a specific embodiment and with a presently preferred arrangement of parts, it will be apparent to those skilled in the art that modifications may be made therein, and it is intended for all such modifications to fall within the scope of the claims attached hereto.

What I claim is:

l. A variable-tone electronic alarm system comprismg:

a pair of terminals;

a variable-voltage source having a voltage control terminal;

a variable-frequency oscillator having a frequencycontrol terminal, said oscillator producing a warning signal in the absence of a signal applied to said frequency-control terminal, and producing a variable-frequency alarm signal when a signal is applied to said frequency-control terminal;

a time-delay network having an output temiinal;

means connecting said variable-voltage source, said variable-frequency oscillator, and said time-delay network in parallel circuit arrangement across said pair of terminals;

means connecting the output of said variable-voltage source to said frequency-control terminal to control the frequency of said variable-frequency oscillator; means connecting the output terminal of said time fiiii ilfiii tffoi s diiifi a Eifibdi i8 vary between predetermined levels thereby causing said variable-frequency source to generate said variable-frequency alarm signal;

a first sound producer;

means connecting said first sound producer to the output circuit of said variable-frequency oscillator to sound said warning signal and said alarm signal;

a source of DC power;

a transmission line including at least a first normally open detector switch for coupling said DC power source to said pair of terminals; and

said warning signal being generated upon the closure of said detector switch, and said alarm signal being generated after a predetermined time interval from the time of closure of said detector switch as determined by said time-delay network.

2. The system of claim 1 and further including:

a second sound producer;

means including a pair of normally-open relay contacts for connecting said second sound producer in parallel-circuit relationship with said first sound producer; and

a relay connected in the output circuit of said timedelay network for closing said relay contacts after said predetermined time interval.

3. The system of claim 2 and further including a power amplifier connected to the output of said variable-frequency oscillator and to said first and second sound producers to amplify the signals generated by said variable-frequency oscillator.

4. The system of claim 3 wherein said warning signal has a single frequency.

5. The system of claim 4 wherein said alarm signal has a variable frequency.

6. The system of claim 5 wherein said first sound producer is positioned inside premises guarded by said alarm system.

7. The system of claim 6 wherein said second sound producer is positioned outside said guarded premises.

8. The system of claim 2 and further including:

a second transmission line comprising at least a second normally open detector switch; and

said second transmission line being connected between said DC power source and said voltagecontrol terminal thereby simultaneously energizing said relay and causing said variable-frequency oscillator to generate said variable-frequency alarm signal immediately after said second detector switch is closed in response to a monitored condition.

9. The system of claim 8 wherein,

said second transmission line includes a silicon-controlled rectifier.

10. The system of claim 1 wherein,

said transmission line includes a silicon-controlled rectifier. 

1. A variable-tone electronic alarm system comprising: a pair of terminals; a variable-voltage source having a voltage control terminal; a variable-frequency oscillator having a frequency-control terminal, said oscillator producing a warning signal in the absence of a signal applied to said frequency-control terminal, and producing a variable-frequency alarm signal when a signal is applied to said frequency-control terminal; a time-delay network having an output terminal; means connecting said variable-voltage source, said variablefrequency oscillator, and said time-delay network in parallel circuit arrangement across said pair of terminals; means connecting the output of said variable-voltage source to said frequency-control terminal to control the frequency of said variable-frequency oscillator; means connecting the output terminal of said time delay-network to said voltage-control terminal to allow the output of said variable-voltage source to vary between predetermined levels thereby causing said variable-frequency source to generate said variable-frequency alarm signal; a first sound producer; means connecting said first sound producer to the output circuit of said variable-frequency oscillator to sound said warning signal and said alarm signal; a source of DC power; a transmission line including at least a first normally open detector switch for coupling said DC power source to said pair of terminals; and said warning signal being generated upon the closure of said detector switch, and said alarm signal being generated after a predetermined time interval from the time of closure of said detector switch as determined by said time-delay network.
 2. The system of claim 1 and further including: a second sound producer; means including a pair of normally-open relay contacts for connecting said second sound producer in parallel-circuit relationship with said first sound producer; and a relay connected in the output circuit of said time-delay network for closing said relay contacts after said predetermined time interval.
 3. The system of claim 2 and further including a power amplifier connected tO the output of said variable-frequency oscillator and to said first and second sound producers to amplify the signals generated by said variable-frequency oscillator.
 4. The system of claim 3 wherein said warning signal has a single frequency.
 5. The system of claim 4 wherein said alarm signal has a variable frequency.
 6. The system of claim 5 wherein said first sound producer is positioned inside premises guarded by said alarm system.
 7. The system of claim 6 wherein said second sound producer is positioned outside said guarded premises.
 8. The system of claim 2 and further including: a second transmission line comprising at least a second normally open detector switch; and said second transmission line being connected between said DC power source and said voltage-control terminal thereby simultaneously energizing said relay and causing said variable-frequency oscillator to generate said variable-frequency alarm signal immediately after said second detector switch is closed in response to a monitored condition.
 9. The system of claim 8 wherein, said second transmission line includes a silicon-controlled rectifier.
 10. The system of claim 1 wherein, said transmission line includes a silicon-controlled rectifier. 